Nuclear emulsions for dark matter detection

On silver halide (AgX) emulsion grains (similar to 200 nm in diameter) for neutrino detection in OPERA project, a latent image center composed of a cluster of >= 4 Ag atoms is formed with similar to 18 electron-hole pairs by current photographic process in each grain. According to the analysis in this paper, AgX emulsion grains (similar to 40 nm) for dark matter detection should behave quite differently, forming a latent image center under such extraordinary condition that as many as similar to 1000 electrons and surplus positive holes are created for similar to 10 femtoseconds (fs) in each grain, causing violent recombination and re-halogenation of Ag clusters. Therefore, it is necessary to strongly reduce the recombination and re-halogenation of Ag clusters in the nuclear emulsions for dark matter detection. Further proposals are made on the design of nuclear emulsions for dark matter detection. (C) 2016 Elsevier Ltd. All rights reserved.